In order to make a case from a corrugated board sheet which has been cut out into predetermined dimensions, it is necessary to prepare a blank, preliminarily, to which required procedures of slotting and creasing have been applied, and a composite device of so-called flexographic printer slotting device is suitably used for such purposes. This device is constituted of units, for example, a flexographic printer, creaser, slotter, etc., which are serially aligned, and designed to carry out the required printing, as well as creasing, slotting, etc. successively against corrugated board sheets which are fed through each of these units.
This invention relates to an improvement of a slotting device (hereinafter referred also to as "slotter"). Therefore, the mechanism of this slotter will first be outlined. FIG. 7 shows a slotter to be incorporated into the flexographic printer slotter, said slotter has a slotting means 10, provided inside thereof, comprising an upper slotting knife 14 and a pair of lower slotting knives 16 disposed, in a vertical relationship. When a corrugated board sheet 12 is fed horizontally through the clearance between the upper slotting knife and the lower slotting knives 16, the desired slotting process can be achieved at the end portion of said sheet 12 along the widthwise direction. It should be noted that two slotters are serially aligned in the line of feeding the corrugated board sheets 12, since a multiplicity of slotting procedures are applied to the corrugated board sheet 12 to form slots along its widthwise direction.
As shown in FIG. 7, an upper slotter shaft 18 and a lower slotter shaft 20 each rotating in opposite directions in synchronization with the speed of feeding the corrugated board sheet 12 are disposed, in a vertical relationship, in the frame (not shown) of the slotter. To the two shafts 18 and 20, rings 22 and 24 are attached, respectively, each comprising an annular plate having a predetermined thickness, to oppose to each other by means of setscrews 26. In this connection, the clearance between the two rings 22 and 24 is preliminarily adjusted such that it may substantially correspond to the thickness of the corrugated board sheet 12, and thus the corrugated board sheet 12 fed to these two rings 22 and 24 is supported therebetween and can be fed downstream of the line of feed.
As shown in FIG. 8, the sectorial upper slotting knife 14 is fixed by means of bolts 28 on the left side of the ring 22 attached to said upper slotter shaft 18, in such a state that its edge 14a may slightly be extended outwardly in the radial direction from the circumferential surface of said ring. Also, a pair of lower slotting knives 16 are fitted by means of bolts 32 on the left side (on the same side that the above upper slotting knife 14 is fixed) of the ring 24 attached to the lower slotter shaft 20, such that a spacer 30 having a thickness slightly greater than that of the upper slotting knife 14 may be sandwiched therebetween. When the upper slotter shaft 18 and the lower slotter shaft 20 are rotated in directions opposing to each other, said upper slotting knife 14 intrudes between the two lower slotting knives 16 to achieve the required slotting process for the corrugated board sheet 12 having been fed to said upper nd lower slotting knives 14 and 16. In this connection, a pair of feed rollers 34 are disposed, in vertical relationships, upstream and downstream of the line relative to the slotting device 10, respectively, as shown in FIG. 7, and the corrugated board sheet 12 is substantially fed by means of these feed rollers.
As described above, it is often required generally to apply printing process to the corrugated board sheet 12 prior to being subjected to the necessary creasing and slotting processes which are required in case making. However, depending on the users of the flexographic printer slotter, it is sometimes necessary to pass on said printed corrugated board sheet 12 to feed it out of the line without application of the slotting process thereto. In such an occasion, it is contemplated that the corrugated board sheet 12 is passed through the slotter and fed out of the line in such a state that the slotting operation may be unapplicable to the corrugated board sheet 12 by ascending the upper slotter shaft 18 to a position at which said upper slotting knife 14 may not be in contact with said sheet 12.
However, for achieving this, not only a complicated mechanism is required for ascending the upper slotter shaft 18, but also the width of the corrugated board sheet 12 which can be fed through said slotter is limited, disadvantageously. To describe in detail, feeding of the corrugated board sheet 12 is carried out by the feed rollers 34 disposed upstream and downstream of the line, respectively, relative to the upper slotter shaft 18 and the lower slotter shaft 20, and the respective rings 22 and 24 attached thereto. Accordingly, when the sheet 12 is subjected to the slotting process, the corrugated board sheet 12 can be fed by the rings 22 and 24 and slotted being supported therebetween, whereby the minimum width of said sheet 12 may be almost correspond to the distance l.sub.1 (see FIG. 7), i.e. the distance from the center of the ring 22 or 24 to the center of the feed roller 34.
However, if the upper slotter shaft 18 is ascended, feeding of the corrugated board sheet 12 by means of the two rings 22 and 24 is no more possible. Therefore, the minimum width of the sheet 12 which can be fed through the slotter may naturally be equal to the distance l.sub.2 (l.sub.2 =2.times.l.sub.1), i.e. the distance from the center of the roller 34 disposed upstream of the line of feeding the sheet 12 to the center of the roller 34 disposed downstream thereof relative to the slotting device 10, and a sheet having a width of shorter than l.sub.2 cannot be fed therethrough, disadvantageously.
It has been attempted to retract all of the rings 22 toward the frame by sliding them along the upper slotter shaft 18 to define a zone in the center of the sheet feeding area, in which the upper slotting knives 14 do not interfere with the corrugated board sheet 12, as another measure for allowing the corrugated board sheet 12 to pass through this zone. However, in such attempt, the sheet 12 cannot be fed by the rings 22 and 24 being supported thereby, and the problem that the width of the corrugated board sheet 12 is limited still remains unsolved.
Thus, it is practiced to feed the corrugated board sheet 12 by means of circumferential surfaces disposed in an area outside of the area where the upper slotting knife 14 provided on the ring 22 are disposed. Such embodiment involves a disadvantage that it can be applied only to a corrugated board sheet 12 having extremely small width. It can also be contemplated to remove all of the upper slotting knives 14 provided in the slotter. In such embodiment, when a corrugated board case of Type A (as stipulated in JIS), for example, is to be prepared, four upper slotting knives 16 are required per one upper slotter shaft 18. Accordingly, eight upper slotting knives 14 must be removed from said shaft to make the operation extremely complicated and time-consuming, disadvantageously.
It can also be contemplated to retract traversely the slotter unit from the flexographic printer slotter mentioned above to be out of the line. However, such embodiment involves problems that a space must be secured for resting the unit having been removed from the line, and that an additional operation is also necessary for stopping the flow of line, which is time-consuming.